Hand-held apparatus for spray cryotherapy

ABSTRACT

A self-contained cryotherapy apparatus adapted to be operated with one hand, using flashing temperature of a cartridge liquefied gas (CO 2 ) sprayed in partly solid phase onto the epidermis. The cartridge support and the ejection and expansion system are aligned therewith and in the axis thereof, inside a housing whereof the median part acts as handle to be grasped by the adult user&#39;s hand, whereof the upper part includes an input for inserting the cartridge with its head down and into the housing axis and striking it or for removing it after use, and whereof the lower part includes a calibrated opening forming a passage for the sprayed gas substantially in the housing axis and elements for controlling its effect on the epidermis.

The invention relates to a self-contained spray cryotherapy apparatusadapted to be manipulated with one hand, particularly efficient in thetreatment of pain, inflammations, or for stimulating the circulation: itis well known that cold brings about a vasomotor reflex and anintensification of the action of draining, and even procures a muscularrelaxation by lowering the muscular tonus: it is well known that coldmakes it possible to obtain a reflex response.

In this respect, it is recalled that cold is much more efficient thanheat, provided, however, that the treatment is effected with an intensecold which must, in addition, provoke a drop in temperature of the zoneto be treated in order to take the epidermis from its normal temperature(about 32° C.) to a temperature included between 2° C. and 5° C. wherethe action of cold is maximum on the cutaneous receptors. Accessorily,it has been observed that the efficiency of the thermal action of thegas sprayed in liquid phase is further increased in large proportions bythe complementary action of the pressure that the flux exerts on theepidermis. The majority of cryotherapy apparatus use as source of coldeither refrigerated air, or more generally liquid nitrogen whose useremains subject to numerous constraints most often limiting the mobilityof the treatment apparatus; in the domain of sport, where cryotherapyfinds one of its major applications, use is currently made of smallaerosols of gas under low pressure whose expansion around a localtraumatism produces cold not exceeding −25° C. with insufficient drop intemperature and speed of cooling.

On the other hand, European Patent EP-0.633.008 in the name of theApplicants has already proposed using as source of cold for thecryotherapy, compressed carbonic anhydride (CO2) of which an intrinsiccharacteristic is to procure a flashing temperature of −78° C. atatmospheric pressure. According to the teachings of this Patent, the useof carbonic anhydride in the form of a liquid/vapour mixture makes itpossible to maintain a constant pressure in the recipient during itsemptying; this pressure which is none other than the saturating vapourpressure, depends directly on the temperature of the recipient. Thus, byexpanding to atmospheric pressure, the carbonic anhydride is in twophases: solid and gaseous. It is the solid phase, also called dry ice,which makes it possible to draw off the maximum of calories at the levelof the epidermis of the patient to be treated. In effect, upon itscontact, the solid carbon dioxide, or dry ice, sublimates, thusevacuating a large quantity of heat. It is therefore essential to drawfrom the recipient the liquid phase of the carbonic anhydride in orderto obtain both an intense cold and a temperature drop which is as rapidas possible.

Patent FR-2.775.589 in the name of the Applicants has already proposed aself-contained, light and portable apparatus capable of producing anintense cold procuring a very rapid temperature drop, and this undermaximum conditions of thermal safety using by way of principal theflashing temperature (of the order of −78° C. at atmospheric pressure)of the carbonic anhydride (CO2) or equivalent in liquid/solid phase; tothat end, the apparatus comprises a reservoir of liquefied CO2 underpressure of which the head is connected to a system of ejection and ofexpansion of the liquid/solid CO2, and comprises members for controllingthe ejection system and for monitoring the temperature of the zone ofuse; this apparatus is noteworthy in that the head of the CO2 reservoiris arranged on the apparatus so that, during the whole period of use,only the liquid part of the CO2 inside the reservoir comes into contactwith said head in order to be drawn off and propelled towards the zoneof use.

This apparatus has been designed to be used by professionals, with thedrawback that it cannot be used by the individual in a domestic context.The present invention therefore relates to an apparatus improved inorder to be used by any adult user simply and without the least dangeroccurring in the event of use under poor conditions.

In this respect, there is proposed, according to the invention, aself-contained cryotherapy apparatus adapted to be manipulated with onehand, using the expansion temperature and pressure of a liquefied gassprayed in at least partially solid phase on a human or animalepidermis, such as CO2 or equivalent, contained under pressure in aremovable cartridge, of which the drawing off head, which is connectedby a support to a controlled system of ejection and of expansion of theliquefied gas, is such that, for the whole duration of a projection,only the liquid part of the gas inside the cartridge comes into contactwith said drawing off head and this apparatus is noteworthy in that thesupport of the cartridge and the controlled ejection and expansionsystem are disposed substantially in line and in the axis of theapparatus, inside an ergonomic housing whose axis corresponds to that ofthe apparatus, of which the median part serves as handle to be graspedby the adult user's hand and comprises a member for controlling thecontrolled gas ejection and expansion system of which the upper partpresents an inlet for introducing into its support the cartridge, headdown and in the axis of the housing, and for striking it or forwithdrawing it after use, and of which the lower part comprises acalibrated opening forming a passage for the sprayed gas substantiallyin the axis of the housing and means for holding the outlet nozzle ofthe controlled ejection and expansion system at the required distancewith respect to the zone of the epidermis to be treated.

It is therefore question of a light, compact apparatus able to operateunder the conditions of intense cold as recalled in the preamble, onlywhen it is grasped in the hand and arranged opposite the zone to betreated in virtually vertical position in order to obtain a projectionof gas in liquid phase. In this respect, any other inclined positionwould lead to spraying the gas in gaseous phase, i.e. at a temperaturewithout danger for the user.

According to several secondary characteristics which will be detailedhereinbelow, the apparatus according to the invention further comprisesa certain number of devices guaranteeing the maximum safety of use; inparticular, it is question of the particular shape of the apparatuswhich fits perfectly in the palm of a clenched hand, procuring anobligatory position for controlling the projection of the cryogenic linethanks to a double electrical control actuated by two different fingersof the hand maintaining the apparatus in vertical position; it is alsofor purposes of safety of use that, according to another importantcharacteristic of the invention, there is provided a device formaintaining the nozzle ejecting the gas at the correct distance in orderthat it be absolutely impossible to cool the epidermis in the treatmentzone below a temperature of 2° C., in any case before the cartridge ofgas equipping the apparatus is totally empty. Finally, and according toa last characteristic, it is provided to complete the precedingprotection systems by temperature sensors procuring within a desiredtime an alarm for the user and/or interrupting the projection in thehypothesis of the epidermis being in danger of necrosis, i.e. cooled tobelow 2° C.

Other characteristics and advantages will appear more readily from thedescription of a cryotherapy apparatus according to the invention forthe general public, given hereinbelow by way of preferred, but in no waylimiting example, with reference to the accompanying drawings, in which:

FIG. 1 shows a general view of the apparatus according to the inventionmaintained vertically in a user's right hand, at the correct distancefrom the epidermis to be treated.

FIG. 2 shows in elevation and in median vertical section the apparatusalong line II/II of FIG. 4, showing the internal structure of themembers as well as their relative position in the apparatus.

FIG. 3 is a view in elevation and in perspective of the apparatus ofwhich one of the half-shells forming the envelope has been removed inorder to show the internal members represented torn away but in relativeposition of functioning.

FIG. 4 is a front (proximal) view in elevation of the assembledapparatus.

FIG. 5 is a rear (distal) view in elevation of the assembled apparatus.

FIG. 6 is a partial representation on a larger scale of the cryogenicchain showing in detail the drawing off head of a gas cartridge mountedon its support inside the apparatus, just before the percussion of itsclosure cap.

FIG. 7 is the same as the preceding Figure, except that the cartridge isshown totally engaged on its support after percussion of its cap.

Referring to the Figures, the cryotherapy apparatus 1 which will bedescribed by way of non-limiting example is particularly intended forso-called domestic use, i.e. by a user who is in principle not aprofessional.

In this respect, FIG. 1 shows a general view of the apparatus 1 graspedin a user's right hand 2 with a view to an application on the epidermis3 of a region to be treated of a gas under pressure—preferably carbonicanhydride (CO2)—, in at least partially solid phase coming from adisposable or re-usable cartridge 4, which is screwed, with its headdown, in a cartridge support provided in the upper part of the apparatus1 in order to maintain and strike an opening cap placing the contents ofthe cartridge 4 in contact with the cryogenic chain which will bedescribed hereinbelow. For safety reasons, the projection of the gas onthe epidermis 3 is controlled by the simultaneous action of a firstswitch 5 controlled by the thumb of the hand 2 and of a second switch 6preferably having the form of a push-trigger 6 disposed in the region ofthe index finger of the hand 2 when the apparatus is grasped in the handas represented in FIG. 1.

The CO2 in liquid/solid phase 7 is ejected via a calibrated opening 8which will be specified hereinbelow, located in the lower part of theapparatus and substantially in its vertical axis. For reasons of safetyand in particular in order to avoid the temperature of the epidermis 3under treatment passing below the critical temperature of 0° C. whichcreates a risk of necrosis of the epidermis, it is necessary to providea minimum distance between the outlet 8 of the gas and the epidermis 3to be treated. To that end, there is provided an excrescence in the formof a prop 9 which extends downwardly substantially in the axis of theapparatus 1 over a sufficient length to procure a suitable spacingbetween the outlet 8 and the epidermis 3, preventing a critical value oftemperature, fixed for example at 2° C., from being attained when allthe gas contained in the cartridge 4 is sprayed. It should be noted thatthe end of the prop 9 advantageously presents a shoe 10 making itpossible to distribute the pressure of the apparatus over the patient'sepidermis and to avoid injuring it during the treatment; in addition,the prop 9 is advantageously located on the proximal side of theapparatus, i.e. towards the user's arm, allowing him/her to bettervisualize the zone of treatment during the whole projection.

In accordance with an essential configuration of the apparatus 1according to the invention, the cryogenic chain shown in FIG. 2 isdisposed substantially in line and in its axis, inside an ergonomichousing 11 of which the median part 12 (FIG. 1) serves as handle to begrasped by the adult user's hand; preferably, the median part 12 of thehousing 11 is in fact substantially convex on the proximal side (i.e.towards the arm of the user), in order to follow the curvature of histhumb; in addition, a recess 13 in the upper part of this side of thehousing 11 allows a movement of approach and of pivoting of the user'sthumb to actuates control of the apparatus as will be stated hereinafterwithout interrupting the contact of the base of the thumb with thehousing 11; on the distal side (i.e. the side most remote from theuser), the median part of the housing is substantially concave in orderto ensure complete grasp by the other four fingers, thus procuring agood grip of the apparatus 1 by one hand 2 of the adult user and to makeit possible, by one or the other of his four fingers, to actuate at thesame time the trigger 6 in order to control projection of gas 7.

According to a preferred embodiment of the apparatus 1, the housing 11is preferably constituted by two half-shells 14, 14′ of identical shape,assembled against one another in the median vertical plane of thehousing 11. The general shape of each half-shell 14, 14′ is representedin plan in FIG. 2, on the inner side of the housing 11; the outer shapeof each half-shell 14, 14′ is shown in front view in FIG. 1 and in sideviews in FIG. 4 for the proximal view and in FIG. 5 for the distal view.

According to an important arrangement of the apparatus in accordancewith the invention, the median part 12 of the housing constituting themember for gripping the apparatus, has a mean section such that it fitsperfectly in an adult's hand but that, reciprocally, it is difficult tohold in a child's hand; in this way, the latter will have difficultiesin holding the apparatus in one hand, which, in addition to theelectrical safety means which will be specified hereinbelow, constitutesa determining element for the safety of children.

With reference to FIGS. 2 and 3, the cryogenic chain of the apparatus 1will now be specified, disposed substantially in line in the axis ofsaid apparatus, and maintained in correct position thanks to housingsprovided inside the half-shells 14 and 14′ in which each of the elementsconstituting the chain fits precisely with the result that, after thetwo half-shells 14, 14′ are assembled, the assembly is totally rigid.

The cryogenic chain successively comprises, in the upper part of theapparatus 1, a support 20 receiving, on the upper side, the drawing offhead 21 of the cartridge 4 via a nut 22 forming connecting piece and, onthe other side, a nut 23 supporting a filter which will be specifiedhereinbelow, an in-line electrovalve 24 intended to place the gas in itsliquid form coming from the cartridge 4 in communication with the gasejection and expansion system constituted by a tube 25 of small innerdiameter of the order of 0.5 mm. In accordance with an importantcharacteristic of the apparatus 1 according to the invention, it isprovided, for questions of safety already taken up in the preamble, tomonitor the sprayed gas thermally; to that end, the tube 25 of theejection and expansion system is associated with a cylindro-conicalsleeve 26 shown in FIG. 2 torn away on a larger scale; the sleeve 26 ismounted coaxially thanks to a radial wedging formed by at least threefins so that the cylindrical part 27 having an inner diameter greaterthan the tube 25, creates an air passage around said tube 25; the apexof the truncated part 28, extending the cylindrical part 27 downwardly,comes flush with the end of the tube 25 forming the gas ejection nozzle29, making an annular space 30 for the passage of air clearly smallerthan in the cylindrical part 27 in order to create by VENTURI effect anaspiration of the ambient air through holes 31 made at the base of thehousing 11 in order to limit in this way the temperature and thepressure in the region of the epidermis 3 to be treated.

According to another embodiment of the invention, it is also possible tomonitor the outlet temperature and pressure of the gas ejection andexpansion system by giving the calibrated opening 8 in the lower part ofthe housing 11 a general nozzle shape, for example in tulip form flaringin the direction of the nozzle 29 and disposed in the same axis, at acorrect distance in order to mix the ambient air sucked through theholes 31 by VENTURI effect generated by the propulsion of the gas.

It goes without saying that the two thermal regulation systems whichhave just been described may be combined in order to adjust thetemperature and pressure of the sprayed gas 7 even more finely.

The members constituting the cryogenic chain inside the apparatus willnow be described in detail, and this with reference to FIGS. 2, 6 and 7.

The cartridge 4 of CO2, medicalized as the case may be, and liquefiedunder a pressure of about 50 bars is in fact a cartridge conventionallycomprising a metal recipient of cylindrical shape, closed at one end,quite similar to but smaller than the cartridges used in prior Patent FR2 775 589 already cited; at the other end, the cartridge is providedwith a drawing off head 21 arranged to cooperate with a support for use20. The drawing off head 21 is constituted by an externally threadedcylindrical connector, a cap 401 which is intended to close thecartridge before it is placed in position in the apparatus, and aninternally and externally threaded nut 22, the internal thread of thenut 22 being screwed on the thread of the connector of the drawing offhead 21 in order to maintain the cap 401 in place. The cartridge 4 is inprinciple disposable taking into account its particular use, but mightalso be refilled if necessary; the cartridges contain CO2 in a quantitysufficient for a treatment of about 15 seconds. The drawing off systemcomprises, as in the prior art, a system for automatic percussion of thecartridge, ensuring the necessary tightness during and after theperforation of the cap 401 for example made of bronze, obturating thecartridge 4. Similarly, the screw pitch of the nut 22 which is screwedabove the drawing off head 21 of the cartridge 4 has been voluntarilychosen from little used pitches so that it is not possible to usecartridges which are not in conformity.

The system of percussion of the cartridges 4 is composed of three partsin accordance with FIGS. 6 and 7. A cylindrical support 20 comprising onthe cartridge side a first internally threaded inlet chamber 201 inwhich is screwed the nut 22 previously mounted on the drawing off head21 obturated by the bronze cap 401; in the axis of this first chamber201 and opening thereinto, a second chamber 202, of smaller diameter,collaborates with the end 221 of the nut 22 of diameter smaller than thethreaded part of said nut in order to ensure total tightness, thanks toan outer O-ring 222 mounted in the area around said end 221, between thecartridge 4 and the rest of the device, as soon as the striker 35perforates the cap 401. The striker 35 forming the second part of thesystem is constituted by a point 36 and is fast with the support 20which may engage in the hollow end part 223 of the nut 22 surroundingthe drawing off head 21 until it comes into contact with the cap 401when the engagement of said nut 22 in the support 20 is sufficient toensure connection of the assembly; at that instant, the point 36 is incontact with the cap 401 and the O-ring 222 is in contact with the wallsof the chamber 202 ensuring its tightness with the drawing off head 21;it then suffices, as shown in FIG. 7, to continue to screw the cartridge4/nut 22 assembly inside the support 20 in order to perforate the cap401; the CO2 can then expand towards the downstream part of the support20, passing firstly through a longitudinal channel 37 provided to thatend in the axis of the striker 35 which opens out in a third coaxialchamber 203 of the support 20 necessary for positioning the percussionsystem and supporting in the flow of the liquid CO2 a filter 38 intendedto retain possible residues contained in the cartridge 4. The filter 38is capped by a nut 23 cooperating with an internal thread of the chamber203 in conventional manner. The nut 23 is axially traversed by a channel231 and it is provided on its downstream face with a threaded axismaking it possible subsequently to implant the input of the electrovalve24.

The latter, chosen from high-pressure electrovalves, allows the openingand closure of an axial channel extending the preceding channel 231 bysimple control of an electromagnet disposed in the axis of theelectrovalve. At the output of the electrovalve 24, is mounted theexpansion tube 25 extending, if necessary, in the cylindrico-conicalsleeve 27 thermally monitoring the flux of CO2. It will also be notedthat, up to the outlet of the electrovalve 24, the CO2 is always in itsliquid form and there is therefore no formation of solid carbon dioxidecapable of preventing the circulation of the fluid; for the purpose ofregulating the outlet flowrate of the liquid CO2, the expansion tube 25is given a very small internal diameter, of the order of 0.5 mm; inorder to avoid the formation of a plug of ice at the outlet of theexpansion tube, a tube made of PTFE is preferably used and, taking intoaccount the pressure of the CO2 of the order of 50 bars at the outlet ofthe cartridge 4, the speed of flow of the CO2 inside the tube 25 issufficiently high to evacuate to the outside the solid carbon dioxide inmicronized particles.

When the cartridge 4 has delivered all its contents in liquid phase, itis necessary to proceed with its replacement or, in accordance withanother embodiment, with its refill. To that end, the cartridge 4 shouldbe withdrawn from its support 20 and the problem is then raised ofpreviously evacuating the residual gas inside the cartridge before it iscompletely withdrawn, in order to avoid a sudden recoil which may, inaddition, be accompanied by a detonation. In order to bleed thecartridge before its withdrawal, there is therefore provided a bleedhole 40 connecting the outside of the chamber 202 disposed most upstreamof the support 20, (i.e. the chamber not comprising the percussionmember 35). This bleed hole 40 (FIG. 6) ensures the bleed of theresidual gas at the moment of withdrawal of the cartridge 4 byunscrewing the nut 22 from its housing in the chamber 201 of the support20; naturally, the internal geometry of this chamber 201 has beenprovided so that, as soon as the uncapped head of the cartridge 4 isdisengaged from the percussion point 36, the residual gas is in contactwith the bleed hole 40, i.e. with the outside, while the length of thethread of the nut 22 still engaged in the chamber 201 is stillsufficient to maintain the assembly rigidly and to avoid any suddenrecoil of the cartridge released from its support; it will thereforesuffice, as soon as the hiss of the gas through the bleed hole 40 isheard, to wait for it to stop before continuing to unscrew the nut 22and remove the cartridge 4, with a view to replacing it, without danger.

According to a particularly important characteristic concerning thesafety of the apparatus, the electrovalve 24 supplied by batteries 41advantageously disposed in a housing 42 (FIGS. 3 and 5) in the upperpart of the distal face of the housing 11 (FIG. 5) and controlled, i.e.switched on, by the simultaneous pressing of the two switches 5 and 6mounted in series in the electrical supply, i.e. between the batteries41 and the coil of the electrovalve 24; as has already been stated, andin order to avoid any manipulation, particularly by children, therelative position of the two switches 5 and 6 projecting on the housing11 is such that, when the median part of said housing is in an adult'shand, the first switch 5, preferably in the form of a push button, comessubstantially under the user's thumb and the second switch 6,advantageously in the form of a trigger, can be actuated by at least oneof the other four fingers of the hand. It has been seen that the twoswitches 5 and 6 were, to that end, located respectively on either sideof the housing 11, diametrally opposite in its median plane.

According to a final characteristic of the invention, the apparatus 1which has just been described may advantageously be completed by acomplementary member for monitoring the temperature of the zone of usein order to avoid the drop in temperature favourable for the treatmentcausing necroses of the tissues; to that end, and according to aparticular embodiment of the invention, it is provided to add atemperature threshold detector 45 coupled to control electronics andcapable of functioning remotely without contact with the zone of use orof care, in accordance with FIGS. 2 and 3. Placed in the lower part ofthe housing 11 for the optics of the detector 45 to be centred in thedirection of the zone to be treated, the preferred temperature thresholddetector has been chosen as an infra-red pyrometer preferably operatingwith a D.C. supply of 12 volts like the electrovalve 24; in practice,the focal distance of the optics of the pyrometer 45 is chosen so thatthe field of vision corresponds as completely as possible to the targetto be measured on the epidermis in order to obtain a correct and precisetemperature reading. To that end, the position of the pyrometer 45 iscalculated precisely in order that its distance to the zone of treatmentnot be either too short, as in that case the heat gradient of the skinbecomes so great that the temperature of the treated zone and thetemperature of the zone scrutinized by the pyrometer are very far fromeach other, with the consequence of rendering the alarm order random,nor be too far, which would almost surely lead to a superpositionbetween the jet of solid carbon dioxide and the infra-red radiation,with the consequence that the pyrometer would read the temperature ofthe jet more surely than that of the zone to be supervised.

According to an accessory characteristic, the threshold detector of thepyrometer 45 is regulated to a temperature of the order of 5° C. inorder to conserve a safety margin; according to a first embodiment, whenthe temperature threshold of the pyrometer 45 is attained, the controlelectronics which are associated therewith warn the user by a sound orvisual signal and/or may cut off the supply of the electrovalve 24,suddenly stopping the projection of the CO2; according to anotherembodiment, the pyrometer 45 can send a sound or visual signal when afirst danger threshold is attained and cut off the electrovalve 24 whena second threshold is attained, for example around 2° C.

The apparatus 1 according to the invention, in accordance with one orthe other of the embodiments which have just been described, may be usedsimply by any adult, non-professional user. To that end, it will sufficefor him to grip in his right hand, for example, the median part 12 ofthe housing 11 of the apparatus, to introduce in the upper part thereofa new cartridge 4 and screw it in its support 20 until percussion of itscap 401 is obtained; the apparatus is then ready to operate and it willsuffice for the adult user to bring it towards the epidermis 3 on whichit is desired to effect a cryotherapy, maintaining it vertically untilthe end 10 of the prop 9 is in contact with the zone to be treated; atthat moment, and the apparatus being maintained vertically, it willsuffice for the user to press simultaneously on the button 5 with histhumb and on the trigger 6 with his index finger in order to trigger offthe electrovalve 24 and therefore the projection 7 of a flow of CO2 inliquid/solid phase. In principle, the cartridge of the apparatus isprovided for one operation, i.e. to take the zone to be treated from atemperature of about 32° C. to a temperature included between 2 and 5°C., and this in about 15 seconds. The thermal safety arrangements of theapparatus have already been seen hereinabove but it will nonetheless beobserved that, when the apparatus is poorly positioned, voluntarily ornot, i.e. when it is no longer in the vertical axis allowing the prop 9to perform its role of separator fully, the diameter of the cartridge 4is such that, very rapidly, the flow propelled via the nozzle 29 of theejection and expansion system is in fact in gaseous form thereforewithout danger for the epidermis from the thermal point of view.

Finally, in accordance with a simpler embodiment of the apparatusaccording to the invention, it is possible to replace the electrovalve24 and all its electrical controls by a purely mechanical device of themanually actuated mechanical valve type. This embodiment, not shown inthe Figures, consists in replacing the electrovalve in the line of thecold by a transverse piston valve actuated by a lever arranged in thezone of grip of the body of the apparatus; in this way it suffices totighten the trigger arranged within reach of the hand holding theapparatus in order to actuate the piston valve, which is, in fact, thesame as placing in contact, upstream, the drawing off head of thecartridge 4 and, downstream, the liquefied gas expansion and ejectionsystem.

In this simplified version of the apparatus, it goes without saying thatthe drawing off head of the cartridge may advantageously be obtained bya contraction of the end of the envelope of the cartridge provided withan adequate thread screwing directly in the cartridge support 20comprising, as in the preceding variant, a percussion member 35; thecartridge thus simplified is obviously provided with a cap cooperatingwith said percussion member, as in the preceding variant.

In this embodiment, a detector of temperature of the zone to be treatedis not necessarily provided, insofar as the quantity of gas contained inthe cartridge in its simplified version is such that it is not possibleto descend this side of the critical temperature even when the contentsof this cartridge are totally ejected.

According to another arrangement which, moreover, is applicable to allthe variants of the apparatus according to the invention, the prop 9making it possible to arrange the nozzle 29 of the ejection system atthe correct distance, may be replaced by a hollowed base of cylindrical,truncated cone or truncated pyramid shape, issing from the lower part ofthe housing 11 and extending downwardly substantially in the axis ofsaid housing over a determined length in order to ensure a sufficientsafety distance as explained hereinabove concerning the prop 9. Thishollow base device presents, furthermore, the advantage of a betterstability of the apparatus at rest and it naturally avoids any error ofpositioning of the apparatus above the zone of the epidermis to betreated.

Functioning of the apparatus in its simplified mechanical version isextremely simple, which renders it particularly suitable for generalpublic use.

1. In a self-contained cryotherapy apparatus adapted to be manipulatedwith one hand, to spray on a human or animal epidermis (3) a gascontained under pressure in a removable cartridge (4), the apparatushaving a drawing off head (21), which is connected by a support (20) toa controlled system of ejection and expansion of the gas, the support(20) of the cartridge and the controlled ejection and expansion systembeing disposed substantially in line along the axis of the apparatus,there being an ergonomic housing (11) surrounding the apparatus whoseaxis corresponds to that of the apparatus, and of which a median partserves as a handle to be grasped by an adult user's hand (2), thehousing (11) having an inlet for introducing to said support saidcartridge (4) head down and along the axis of the housing (11) and forstriking the cartridge and withdrawing it after use, a lower part ofsaid housing comprising a calibrated opening (8) forming a passage forthe sprayed gas substantially along the axis of the housing, and means(9) for holding an outlet nozzle (29) of the controlled ejection andexpansion system at a required distance with respect to the zone of theepidermis to be treated; the improvement comprising an electrovalve (24)in line with the tube (25) for ejection of the gas, and two switches (5,6) adapted to be actuated by the user's hand (2) and mounted in seriesin an electrical supply (41) of the electrovalve (24), the actuation ofthe electrovalve requiring the simultaneous pressing of the two switches(5, 6) by the user's hand (2) to actuate the electrical supply (41) ofthe electrovalve (24), the position of the two switches (5, 6) on thehousing (11) being such that when the median part (12) of said housingis in an adult's hand (2), a first switch (5) comes under the user'sthumb and the second switch (6) can be actuated by one or more of theother four fingers of the user's hand (2), said housing (11) beingshaped to be substantially convex on a proximal side facing the user inorder to follow the curvature of the user's thumb, a recess (13) in anupper portion of the housing (11) allowing the movement of approach ofthe thumb without interrupting the contact of the base of the thumb withthe housing, the housing being substantially concave on a distal sideaway from the user for a complete grasp by a finger or fingers of theuser.
 2. Apparatus according to claim 1, characterized in that the tube(25) of the liquefied gas ejection and expansion system is a tube of aninner diameter of about 0.5 mm.
 3. Apparatus according to claim 1,characterized in that the means for holding the nozzle (29) of theejection system at the required distance from the epidermis (3) to betreated are constituted by an excrescence of a prop (9) issuing from thelower part of the housing (11) and extending downwardly, substantiallyparallel to the axis of said housing over a determined length in orderto maintain the required distance, when the apparatus (1) is positionedopposite the epidermis (3).
 4. Apparatus according to claim 1,characterized in that the cartridge (4) comprises a tubular body closedat one end and presenting at the other end a drawing off head (21)constituted by an externally threaded cylindrical connector, by a cap(401) which is intended to close the cartridge before it is placed inposition in the apparatus.
 5. Apparatus according to claim 4,characterized in that the drawing off head (21) of the cartridge isprovided with an internally and externally threaded nut (22), the innerthread of the nut (22) being screwed on the thread of the connector ofthe drawing off head (21) in order to hold the cap (401) in place. 6.Apparatus according to claim 4, characterized in that the cartridge (4)is connected to the cartridge support (20) in the apparatus by screwingso as firstly to bring the cap (401) into contact with a fixedpercussion member (35), extending in the axis of the support (10), thento pierce said cap (401) ensuring tightness of the assembly in order todraw off the gas in liquid phase via an axial channel (37) traversingright through the percussion device, connected downstream at its freeend to the controlled expansion system, a bleed hole (40) between theinner space of the support (20) and the outside being provided radiallyin that part of said support (20) not comprising the percussion member(35) in order to bleed the residual gas in the empty cartridge duringits unscrewing and before it is completely disconnected from theapparatus.
 7. Apparatus according to claim 1, which further comprisesmeans for monitoring the projected gas which consist in surrounding theoutlet tube (25) of the ejection and expansion system by acylindrico-conical sleeve (26) mounted coaxially thanks to a radialwedge of which the cylindrical part (27) has an inner diameter largerthan a tube (25) in order to create a passage of air all around saidtube and of which the apex of the truncated part (28) extending thecylindrical part (27) comes flush with the end of the tube (25) formingan ejection nozzle (29) arranging an annular space for the passage ofair clearly smaller than in the cylindrical part (27) in order to createby VENTURI effect a suction of the ambient air through openings (31)made at the base of the housing (11) and thus to limit the temperatureand pressure in the region to be treated.
 8. Apparatus according toclaim 1, which further comprises means for monitoring the projected gasconstituted by the arrangement of the calibrated opening (8) in thelower part of the housing (11) having the general shape of a nozzle inthe form of a tulip flared in the direction of the nozzle (29) of thetube (25) and is disposed in the same axis, at the correct distance fromsaid nozzle and via openings (31) made at the base of the housing (11)so as to mix with the liquefied gas in the course of expansion of theambient air sucked through openings (31) by VENTURI effect created bythe propulsion of the gas.
 9. Apparatus according to claim 1, whichfurther comprises a means for thermally monitoring the epidermis (3)which is a detector (45) for detecting the temperature of the epidermis(3) acting without contact therewith.
 10. Apparatus according to claim9, characterized in that the detector is an infrared pyrometer (45). 11.Apparatus according to claim 10, characterized in that the focaldistance of the infrared pyrometer (45) is such, on the one hand, thatthere is no interaction with the spraying of the liquefied gas, and, onthe other hand, that the precise measurement of temperature is effectedwhen the apparatus (1) is positioned at a suitable distance for the useenvisaged.
 12. Apparatus according to claim 10, characterized in thatthe infrared pyrometer (45) is coupled to a visual and/or sound alarmwhen the drop in temperature of the zone of use reaches a predeterminedthreshold, the pyrometer (45) in that case being able to automaticallycut off the electrical supply of the electrovalve (24).